The moving components of a motorcycle engine require lubrication to preserve and extend their useful lives. Many of the moving components are located in the crankcase and rocker box of the engine. In operation, the oil used for lubricating the components in the crankcase (i.e. the connecting rod, crankshaft, and associated links) is atomized and sprayed thereon. As a result, a fine oil mist exists in the air in the crankcase. Some vaporized oil also exists within the crankcase because of the heat conducted from the combustion chamber. The air in the crankcase therefore holds a noticeable amount of atomized and vaporized oil.
The oil mixed in the air represents a problem because the crankcase must be vented for proper operation. If the crankcase were not vented, the trapped air would fluctuate in pressure as the pistons reciprocate. Since it is the pressure difference between the combustion chamber and the crankcase that drives the pistons down during the power stroke, the pressure of the trapped gas would oppose the power stroke and decrease the performance of the engine proportionally.
Venting the crankcase, though, creates other difficulties. Namely, as the piston moves toward the crankcase during the power stroke, the air being vented entrains the atomized and vaporized oil. If the oil is not separated from the air before being vented, the engine eventually runs dry and fails for lack of lubrication. For this reason, engine manufacturers typically include an oil/air separator, an air cleaner, or both in the crankcase vent subsystem. These devices minimize the amount of oil vented from the crankcase with the air. But they are not perfect.
Currently available oil/air separators and air cleaners tend to allow some oil to escape from the crankcase with the air. Once outside of the engine, the oil fouls the motorcycle and the rider thereon. The oil/air separators and cleaners of the prior art also add to the weight of the engine and tend to decrease the acceleration and handling characteristics of the bike according to the extra weight. Further, because a motorcycle engine must be small enough to fit within the frame of the motorcycle and to allow the rider to straddle the same, even small increases in the size of the engine are detrimental. Yet currently available oil/air separators and air cleaners increase the overall size of the engine.
A need therefore exists for improved oil/air separators.